<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>基本选择器</title>
</head>
<body>
<div id="div1">div1</div>
<div class="cls">div2</div>
<div class="cls">div3</div>
<span>span</span>
</body>
<script src="js/jquery-3.3.1.min.js"></script>
<script>
   let divs = $("div");

   let divOne = $("#div1");

   let divCls = $(".cls");

    $(".cls,span").css("backgroundColor","green");

</script>
</html>